The IEEE standard, "IEEE 1394 Standard For A High Performance Serial Bus," Draft ratified in 1995, is an international standard for implementing an inexpensive high-speed serial bus architecture which supports both asynchronous and isochronous format data transfers. Isochronous data transfers are real-time transfers which take place such that the time intervals between significant instances have the same duration at both the transmitting and receiving applications. Each packet of data transferred isochronously is transferred in its own time period. The IEEE 1394-1995 standard bus architecture provides multiple channels for isochronous data transfer between applications. A six bit channel number is broadcast with the data to ensure reception by the appropriate application. This allows multiple applications to simultaneously transmit isochronous data across the bus structure. Asynchronous transfers are traditional data transfer operations which take place as soon as possible and transfer an amount of data from a source to a destination.
The IEEE 1394-1995 standard provides a high-speed serial bus for interconnecting digital devices thereby providing a universal I/O connection. The IEEE 1394-1995 standard defines a digital interface for the applications thereby eliminating the need for an application to convert digital data to analog data before it is transmitted across the bus. Correspondingly, a receiving application will receive digital data from the bus, not analog data, and will therefore not be required to convert analog data to digital data. The cable required by the IEEE 1394-1995 standard is very thin in size compared to other bulkier cables used to connect such devices. Devices can be added and removed from an IEEE 1394-1995 bus while the bus is active. If a device is so added or removed, the bus will then automatically reconfigure itself for transmitting data between the then existing nodes. A node is considered a logical entity with a unique address on the bus structure. Each node provides an identification ROM, a standardized set of control registers and its own address space.
The IEEE 1394-1995 standard defines a protocol as illustrated in FIG. 1. This protocol includes a serial bus management block 10 coupled to a transaction layer 12, a link layer 14 and a physical layer 16. The physical layer 16 provides the electrical and mechanical connection between a device or application and the IEEE 1394-1995 cable. The physical layer 16 also provides arbitration to ensure that all devices coupled to the IEEE 1394-1995 bus have access to the bus as well as actual data transmission and reception. The link layer 14 provides data packet delivery service for both asynchronous and isochronous data packet transport. This supports both asynchronous data transport, using an acknowledgement protocol, and isochronous data transport, providing real-time guaranteed bandwidth protocol for just-in-time data delivery. The transaction layer 12 supports the commands necessary to complete asynchronous data transfers, including read, write and lock. The serial bus management block 10 contains an isochronous resource manager for managing isochronous data transfers. The serial bus management block 10 also provides overall configuration control of the serial bus in the form of optimizing arbitration timing, guarantee of adequate electrical power for all devices on the bus, assignment of the cycle master, assignment of isochronous channel and bandwidth resources and basic notification of errors.
Televisions used in consumer electronics systems typically have limited sound capability. Instead, high quality audio capability is achieved within typical home consumer electronics systems or configurations by connecting a separate audio amplifier component to the television. This audio amplifier will then amplify audio from a television or other video receiving device such as a video cassette recorder (VCR), and send the amplified audio signal to an attached set of speakers.
Corresponding audio and video streams of data are combined into MPEG compressed streams of data for transmission between devices. Audio/video streams of data are also stored in an MPEG compressed format in order to reduce the amount of storage space required for the stream of data. A decompression engine is required in order to decompress an MPEG compressed stream of data at the receiving component. Accordingly, in a consumer electronics system as described above, each component receiving the MPEG data stream must include an MPEG decompression engine. Both the television and the audio amplifier would need to include an MPEG decompression engine in order to separately decompress the video and audio components of the MPEG data stream.
A consumer entertainment system including a settop box, a satellite dish, a television and an audio amplifier is illustrated in FIG. 2. The settop box 22 is coupled to receive an MPEG stream of data from the satellite dish 30. The settop box 22 includes an MPEG decompression engine to decompress the MPEG stream of data. The settop box 22 is coupled to the television 20 to separately provide the television 20 with the video component from the MPEG stream of data through an analog video interface. The settop box 22 is also coupled to the audio amplifier 24 to separately provide the audio amplifier 24 with the audio component from the MPEG stream of data through an analog audio interface. The audio amplifier 24 is coupled to the speakers 26 and 28 for providing the amplified audio signal to be played on the speakers.
The settop box 22 decompresses an MPEG stream of data received from the satellite dish 30 and separates the audio and video components. The audio and video components are then transmitted from the settop box 22 to the television 20 and the audio amplifier 24, respectively, in order that the video is displayed on the television 20 while the corresponding audio is played from the speakers 26 and 28. The audio and video components are transmitted from the settop box 22 through separate analog interfaces to the appropriate components.
In the configuration illustrated in FIG. 2, only the settop box 22 is required to include an MPEG decompression engine. This decompression engine within the settop box 22 is used to decompress both the audio and video components within the MPEG stream of data. The settop box 22 includes separate analog interfaces for transmitting the audio data to the audio amplifier 24 and the video data to the television 20.
What is needed is a system which includes a single decompression engine for decompressing an MPEG stream of data and a single interface through which the audio component and the video component can be transmitted.